The OR logical operator chains multiple criteria together. A valid operand
of an OR operator must be one of: TRUE,
FALSE, and NULL. The OR operator has
a lower precedence than the AND operator.

NULL represents unknown. Therefore, if one operand is NULL
and the other operand is TRUE the result is TRUE, because
one TRUE operand is sufficient for a TRUE result. If one
operand is NULL and the other operand is either FALSE or
NULL, the result is NULL (unknown).

The following table shows how the OR operator is evaluated based on its two operands: